sedimentary
Ferruginous Sandstone
Arenite with Iron-Oxide Cement (SiO2 with Fe2O3/FeO(OH))
Hardness: 6-7 (Mohs scale) for grains; Color: reddish-brown to rust orange; Luster: earthy or dull; Structure: clastic texture with visible sand grains; Cleavage: none.
- Hardness
- 6-7 (Mohs scale) for grains
- Color
- reddish-brown to rust orange
- Luster
- earthy or dull
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Physical properties
Hardness: 6-7 (Mohs scale) for grains; Color: reddish-brown to rust orange; Luster: earthy or dull; Structure: clastic texture with visible sand grains; Cleavage: none.
Formation & geological history
Formed through the accumulation of sand-sized quartz grains in high-energy environments like rivers or deserts, subsequently cemented together by iron oxides (hematite or limonite) precipitated from groundwater.
Uses & applications
Commonly used as building stone, decorative landscaping gravel, and occasionally as a source of iron ore if concentration is high enough.
Geological facts
The deep red color is primarily due to the oxidation of iron minerals, essentially making this a 'rusted' rock. It is the primary component of many famous landscapes, such as those in Sedona, Arizona and the Red Rocks of Colorado.
Field identification & locations
Identify by its gritty texture and the fact that it will not fizz with acid (unlike limestone). It is commonly found in sedimentary basins and arid regions globally.
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